U.S. patent application number 11/998743 was filed with the patent office on 2008-04-17 for helical coil apparatus for ablation of tissue.
Invention is credited to Richard H. Comben, Michael F. Hoey, Peter M.J. Mulier.
Application Number | 20080091194 11/998743 |
Document ID | / |
Family ID | 26784524 |
Filed Date | 2008-04-17 |
United States Patent
Application |
20080091194 |
Kind Code |
A1 |
Mulier; Peter M.J. ; et
al. |
April 17, 2008 |
Helical coil apparatus for ablation of tissue
Abstract
A surgical apparatus for delivering a conductive fluid to a
target site for subsequent formation of a virtual electrode to
ablate bodily tissue at the target site by applying a current to
the delivered conductive fluid. The surgical apparatus includes an
elongated device forming a helical needle. The helical needle is
configured to engage bodily tissue and is hollow for delivering
conductive fluid from a fluid source. Finally, the helical needle
terminates in a needle tip. In one preferred embodiment, an
electrode is associated with the helical needle for applying a
current to conductive fluid delivered from the helical needle.
During use, following delivery of conductive fluid, the electrode
applies a current to the delivered conductive fluid for creating a
virtual electrode. The virtual electrode ablates bodily tissue
contacted by the conductive fluid.
Inventors: |
Mulier; Peter M.J.;
(Stillwater, MN) ; Hoey; Michael F.; (Shoreview,
MN) ; Comben; Richard H.; (St. Paul, MN) |
Correspondence
Address: |
James R. Keogh;Medtronic, Inc.
710 Medtronic Parkway
Minneapolis
MN
55432
US
|
Family ID: |
26784524 |
Appl. No.: |
11/998743 |
Filed: |
November 30, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11169275 |
Jun 28, 2005 |
7309325 |
|
|
11998743 |
Nov 30, 2007 |
|
|
|
10014388 |
Oct 22, 2001 |
6911019 |
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11169275 |
Jun 28, 2005 |
|
|
|
09347752 |
Jul 6, 1999 |
6537248 |
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10014388 |
Oct 22, 2001 |
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60091969 |
Jul 7, 1998 |
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Current U.S.
Class: |
606/41 |
Current CPC
Class: |
A61B 2018/1435 20130101;
A61B 2018/1472 20130101; A61B 2218/002 20130101; A61B 18/1477
20130101 |
Class at
Publication: |
606/041 |
International
Class: |
A61B 18/14 20060101
A61B018/14 |
Claims
1. A medical procedure comprising: providing a medical device
comprising first and second helical coils configured to engage
bodily tissue, the first and second helical coils comprising at
least one opening for delivery of a conductive fluid to a tissue
treatment site, the first and second helical coils wound parallel
to one another, the first and second helical coils configured to
apply electric current to bodily tissue, the first helical coil
serving as a first electrode of a bipolar electrode configuration
and the second helical coil serving as the second electrode of the
bipolar electrode configuration; maneuvering the first and second
helical coils into contact with tissue; delivering the conductive
fluid to the tissue; and applying electric current to the
tissue.
2. The medical procedure according to claim 1 wherein the first
coil comprises a plurality of conductive fluid delivery
openings.
3. The medical procedure according to claim 2 wherein the plurality
of conductive fluid delivery openings are located along the length
of the first coil.
4. The medical procedure according to claim 1 wherein the
conductive fluid delivery opening of the first coil comprises a
hole.
5. The medical procedure according to claim 1 wherein the
conductive fluid delivery opening of the first coil comprises a
slit.
6. The medical procedure according to claim 1 wherein the second
coil comprises a plurality of conductive fluid delivery
openings.
7. The medical procedure according to claim 6 wherein the plurality
of conductive fluid delivery openings are located along the length
of the second coil.
8. The medical procedure according to claim 1 wherein the
conductive fluid delivery opening of the second coil comprises a
hole.
9. The medical procedure according to claim 1 wherein the
conductive fluid delivery opening of the second coil comprises a
slit.
10. The medical procedure according to claim 1 wherein the first
coil is provided by a first needle and the second coil is provided
by a second needle.
11. The medical procedure according to claim 10 wherein the first
needle is hollow and the second needle is hollow.
12. A medical procedure comprising: providing a medical device
comprising first and second helical coils configured to engage
bodily tissue, the first and second helical coils comprising at
least one opening for delivery of a conductive fluid to a tissue
treatment site, the second helical coil concentrically disposed
within the first helical coil, the first and second helical coils
configured to apply electric current to bodily tissue, the first
helical coil serving as a first electrode of a bipolar electrode
configuration and the second helical coil serving as the second
electrode of the bipolar electrode configuration; maneuvering the
first and second helical coils into contact with tissue; delivering
the conductive fluid to the tissue; and applying electric current
to the tissue.
13. The medical procedure according to claim 12 wherein the first
coil comprises a plurality of conductive fluid delivery
openings.
14. The medical procedure according to claim 13 wherein the
plurality of conductive fluid delivery openings are located along
the length of the first coil.
15. The medical procedure according to claim 12 wherein the
conductive fluid delivery opening of the first coil comprises a
hole.
16. The medical procedure according to claim 12 wherein the
conductive fluid delivery opening of the second coil comprises a
slit.
17. The medical procedure according to claim 12 wherein the second
coil comprises a plurality of conductive fluid delivery
openings.
18. The medical procedure according to claim 17 wherein the
plurality of conductive fluid delivery openings are located along
the length of the second coil.
19. The medical procedure according to claim 12 wherein the
conductive fluid delivery opening of the second coil comprises a
hole.
20. The medical procedure according to claim 12 wherein the
conductive fluid delivery opening of the second coil comprises a
slit.
21. The medical procedure according to claim 12 wherein the first
coil is provided by a first needle and the second coil is provided
by a second needle.
22. The medical procedure according to claim 21 wherein the first
needle is hollow and the second needle is hollow.
23. The medical procedure according to claim 12 wherein the second
coil has an outer diameter less than an inner diameter defined by
the first coil.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 11/169,275, filed, Jun. 28, 2005, which is a
continuation of U.S. patent application Ser. No. 10/014,388, filed,
Oct. 22, 2001, now U.S. Pat. No. 6,911,019, which is a continuation
of U.S. patent application Ser. No. 09/347,752, filed Jul. 6, 1999,
now U.S. Pat. No. 6,537,248, which claims the benefit of U.S.
Provisional Application No. 60/091,969, filed on Jul. 7, 1998,
which are incorporated by reference herein in their entirety.
FIELD OF THE INVENTION
[0002] The present invention relates generally to an apparatus for
creating a virtual electrode. More particularly, the present
invention relates to an apparatus for the creation of a virtual
electrode that is useful for the ablation of soft tissue and
neoplasms.
BACKGROUND OF THE PRESENT INVENTION
[0003] The utilization of an electric current to produce an
ameliorative effect on a bodily tissue has a long history,
reportedly extending back to the ancient Greeks. The effects on
bodily tissue from an applied electric current, and thus the
dividing line between harmful and curative effects, will vary
depending upon the voltage levels, current levels, the length of
time the current is applied, and the tissue involved. One such
effect resulting from the passage of an electric current through
tissue is heat generation.
[0004] Body tissue, like all non-superconducting materials,
conducts current with some degree of resistance. This resistance
creates localized heating of the tissue through which the current
is being conducted. The amount of heat generated will vary with the
power P deposited in the tissue, which is a function of the product
of the square of the current I and the resistance R of the tissue
to the passage of the current through it (P=I.sup.2R.).
[0005] As current is applied to tissue, then, heat is generated due
to the inherent resistance of the tissue. Deleterious effects in
the cells making up the tissue begin to occur at about 42.degree.
Celsius. As the temperature of the tissue increases due to heat
generated by the tissue's resistance, the tissue will undergo
profound changes and eventually, as the temperature becomes high
enough, that is, generally greater than 45.degree. C., the cells
will die. The zone of cell death is known as a lesion and the
procedure followed to create the lesion is commonly called an
ablation. As the temperature increases beyond cell death
temperature, complete disintegration of the cell walls and cells
caused by boiling off of the tissue's water can occur. Cell death
temperatures can vary somewhat with the type of tissue to which the
power is being applied, but generally will begin to occur within
the range of 45.degree. to 60.degree. C., though actual cell death
of certain tissue cells may occur at a higher temperature.
[0006] In recent times, electric current has found advantageous use
in surgery, with the development of a variety of surgical
instruments for cutting tissue or for coagulating blood. Still more
recently, the use of alternating electric current to ablate, that
is, kill, various tissues has been explored. Typically, current
having a frequency from about 3 kilohertz to about 300 gigahertz,
which is generally known as radiofrequency or radiofrequency (RF)
current, is used for this procedure. Destruction, that is, killing,
of tissue using an RF current is commonly known as radiofrequency
ablation. Often radiofrequency ablation is performed as a minimally
invasive procedure and is thus known as radiofrequency catheter
ablation because the procedure is performed through and with the
use of a catheter. By way of example, radiofrequency catheter
ablation has been used to ablate cardiac tissue responsible for
irregular heart beats or arrythmias.
[0007] The prior art applications of current to tissue have
typically involved applying the current using a "dry" electrode.
That is, a metal electrode is applied to the tissue desired to be
affected and a generated electric current is passed through the
electrode to the tissue. A commonly known example of an instrument
having such an operating characteristic is an electrosurgical
instrument known as a "bovie" knife. This instrument includes a
cutting/coagulating blade electrically attached to a current
generator. The blade is applied to the tissue of a patient and the
current passes through the blade into the tissue and through the
patient's body to a metal base electrode or ground plate usually
placed underneath and in electrical contact with the patient. The
base electrode is in turn electrically connected to the current
generator so as to provide a complete circuit.
[0008] As the current from the bovie knife passes from the blade
into the tissue, the resistance provided by the tissue creates
heat. In the cutting mode, a sufficient application of power
through the bovie knife to the tissue causes the fluid within the
cell to turn to steam, creating a sufficient overpressure so as to
burst the cell walls. The cells then dry up, desiccate, and
carbonize, resulting in localized shrinking and an opening in the
tissue. Alternatively, the bovie knife can be applied to bleeding
vessels to heat and coagulate the blood flowing therefrom and thus
stop the bleeding.
[0009] As previously noted, another use for electrical instruments
in the treatment of the body is in the ablation of tissue. To
expand further on the brief description given earlier of the
ablation of cardiac tissue, it has long been known that a certain
kind of heart tissue known as sino-atrial and atrio-ventricular
nodes spontaneously generate an electrical signal that is
propagated throughout the heart along conductive pathways to cause
it to beat. Occasionally, certain heart tissue will "misfire,"
causing the heart to beat irregularly. If the errant electrical
pathways can be determined, the tissue pathways can be ablated and
the irregular heartbeat remedied. In such a procedure, an electrode
is placed via a catheter into contact with the tissue and then
current is applied to the tissue via the electrode from a generator
of RF current. The applied current will cause the tissue in contact
with the electrode to heat. Power will continue to be applied until
the tissue reaches a temperature where the heart tissue dies,
thereby destroying the errant electrical pathway and the cause of
the irregular heartbeat.
[0010] Another procedure using RF ablation is transurethral needle
ablation, or TUNA, which is used to create a lesion in the prostate
gland for the treatment of benign prostatic hypertrophy (BPH) or
the enlargement of the prostate gland. In a TUNA procedure, a
needle having an exposed conductive tip is inserted into the
prostate gland and current is applied to the prostate gland via the
needle. As noted previously, the tissue of the prostate gland heats
locally surrounding the needle tip as the current passes from the
needle to the base electrode. A lesion is created as the tissue
heats and the destroyed cells may be reabsorbed by the body,
infiltrated with scar tissue, or just become non-functional.
[0011] While there are advantages and uses for such "dry" electrode
instruments, there are also several notable disadvantages. One of
these disadvantages is that during a procedure, coagulum--dried
blood cells and tissue cells--will form on the electrode engaging
the tissue. Coagulum acts as an insulator and effectively functions
to prevent current transfer from the blade to the tissue. This
coagulum "insulation" can be overcome with more voltage so as to
keep the current flowing, but only at the risk of arcing and
injuring the patient. Thus, during surgery when the tissue is cut
with an electrosurgical scalpel, a build-up of coagulated blood and
desiccated tissue will occur on the blade, requiring the blade to
be cleaned before further use. Typically, cleaning an
electrode/scalpel used in this manner will involve simply scraping
the dried tissue from the electrode/scalpel by rubbing the scalpel
across an abrasive pad to remove the coagulum. This is a tedious
procedure for the surgeon and the operating staff since it requires
the "real" work of the surgery to be discontinued while the
cleaning operation occurs. This procedure can be avoided with the
use of specially coated blades that resist the build up of
coagulum. Such specialty blades are costly, however.
[0012] A second disadvantage of the dry electrode approach is that
the electrical heating of the tissue creates smoke that is now
known to include cancer-causing agents. Thus, preferred uses of
such equipment will include appropriate ventilation systems, which
can themselves become quite elaborate and quite expensive.
[0013] A further, and perhaps the most significant, disadvantage of
dry electrode electrosurgical tools is revealed during cardiac
ablation procedures. During such a procedure, an electrode that is
otherwise insulated but having an exposed, current carrying tip is
inserted into the heart chamber and brought into contact with the
inner or endocardial side of the heart wall where the ablation is
to occur. The current is initiated and passes from the current
generator to the needle tip electrode and from there into the
tissue so that a lesion is created. Typically, however, the lesion
created by a single insertion is insufficient to cure the irregular
heartbeat because the lesion created is of an insufficient size to
destroy the errant electrical pathway. Thus, multiple needle
insertions and multiple current applications are almost always
required to ablate the errant cardiac pathway, prolonging the
surgery and thus increasing the potential risk to the patient.
[0014] This foregoing problem is also present in TUNA procedures,
which similarly require multiple insertions of the needle electrode
into the prostate gland. Failing to do so will result in the
failure to create a lesion of sufficient size otherwise required
for beneficial results. As with radiofrequency catheter ablation of
cardiac tissue, then, the ability to create a lesion of the
necessary size to alleviate BPH symptoms is limited and thus
requires multiple insertions of the electrode into the
prostate.
[0015] A typical lesion created with a dry electrode using RF
current and a single insertion will normally not exceed one
centimeter in diameter. This small size--often too small to be of
much or any therapeutic benefit--stems from the fact that the
tissue surrounding the needle electrode tends to desiccate as the
temperature of the tissue increases, leading to the creation of a
high resistance to the further passage of current from the needle
electrode into the tissue, all as previously noted with regard to
the formation of coagulum on an electrosurgical scalpel. This high
resistance-more properly termed impedance since typically an
alternating current is being used-between the needle electrode and
the base electrode is commonly measured by the RF current
generator. When the measured impedance reaches a pre-determined
level, some prior art generators will discontinue current
generation. Discontinuance of the ablation procedure under these
circumstances is necessary to avoid injury to the patient.
[0016] Thus, a typical procedure with a dry electrode may involve
placing the needle electrode at a first desired location;
energizing the electrode to ablate the tissue; continue applying
current until the generator measures a high impedance and shuts
down; moving the needle to a new location closely adjacent to the
first location; and applying current again to the tissue through
the needle electrode. This cycle of electrode placement, electrode
energization, generator shut down, electrode re-emplacement, and
electrode re-energization, will be continued until a lesion of the
desired size has been created. As noted, this increases the length
of the procedure for the patient. Additionally, multiple insertions
increases the risk of at least one of the placements being in the
wrong location and, consequently, the risk that healthy tissue may
be undesirably affected while diseased tissue may be left
untreated. The traditional RF ablation procedure of using a dry
ablation therefore includes several patient risk factors that both
patient and physician would prefer to reduce or eliminate.
[0017] The therapeutic advantages of RF current could be increased
if a larger lesion could be created safely with a single
positioning of the current-supplying electrode. A single
positioning would allow the procedure to be carried out more
expeditiously and more efficiently, reducing the time involved in
the procedure. Larger lesions can be created in at least two ways.
First, simply continuing to apply current to the patient with
sufficiently increasing voltage to overcome the impedance rises
will create a larger lesion, though almost always with undesirable
results to the patient. Second, a larger lesion can be created if
the current density, that is, the applied electrical energy, could
be spread more efficiently throughout a larger volume of tissue.
Spreading the current density over a larger tissue volume would
correspondingly cause a larger volume of tissue to heat in the
first instance. That is, by spreading the applied power throughout
a larger tissue volume, the tissue would heat more uniformly over a
larger volume, which would help to reduce the likelihood of
generator shutdown due to high impedance conditions. The applied
power, then, will cause the larger volume of tissue to be ablated
safely, efficiently, and quickly.
[0018] Research conducted under the auspices of the assignee of the
present invention has focused on spreading the current density
throughout a larger tissue volume through the creation,
maintenance, and control of a "virtual electrode" within or
adjacent to the tissue to be ablated. A virtual electrode can be
created by the introduction of a conductive fluid, such as isotonic
or hypertonic saline, into or onto the tissue to be ablated. The
conductive fluid will facilitate the spread of the current density
substantially equally throughout the extent of the flow of the
conductive fluid, thus creating an electrode--a virtual
electrode--substantially equal in extent to the size of the
delivered conductive fluid. RF current can then be passed through
the virtual electrode into the tissue.
[0019] A virtual electrode can be substantially larger in volume
than the needle tip electrode typically used in RF interstitial
ablation procedures and thus can create a larger lesion than can a
dry, needle tip electrode. That is, the virtual electrode spreads
or conducts the RF current density outward from the RF current
source--such as a current carrying needle, forceps or other current
delivery device--into or onto a larger volume of tissue than is
possible with instruments that rely on the use of a dry electrode.
Stated otherwise, the creation of the virtual electrode enables the
current to flow with reduced resistance or impedance throughout a
larger volume of tissue, thus spreading the resistive heating
created by the current flow through a larger volume of tissue and
thereby creating a larger lesion than could otherwise be created
with a dry electrode.
[0020] While the efficacy of RF current ablation techniques using a
virtual electrode has been demonstrated in several studies, the
currently available instruments useful in such procedures lags
behind the research into and development of hoped-for useful
treatment modalities for the ablation of soft tissue and
malignancies.
[0021] It would be desirable to have an apparatus capable of
creating a virtual electrode for the controlled application of
tissue ablating RF electric current to a tissue of interest so as
to produce a lesion of desired size and configuration.
SUMMARY OF THE INVENTION
[0022] One aspect of the present invention provides a surgical
apparatus for delivering conductive fluid to a target site for
subsequent formation of a virtual electrode to ablate bodily tissue
at the target site by applying a current to the delivered
conductive fluid. The surgical apparatus comprises an elongated
device forming a helical needle assembly. The helical needle
assembly includes a helical needle configured to engage bodily
tissue. The helical needle is hollow for delivering conductive
fluid from a fluid source and forms a needle tip. In one preferred
embodiment, an electrode is associated with the helical needle
assembly for applying a current to conductive fluid delivered from
the helical needle assembly. During use, the helical needle
assembly is maneuvered into contact with bodily tissue at a desired
location. Conductive fluid is delivered to the tissue via the
hollow helical needle. The electrode applies a current to the
so-delivered conductive fluid, thereby creating a virtual electrode
for ablating the bodily tissue.
[0023] Another aspect of the present invention relates to a
surgical system for creating a virtual electrode to ablate bodily
tissue. The system includes a fluid source, a current source and a
surgical instrument. The fluid source maintains a supply of
conductive fluid. The current source is configured to selectively
supply a current. Finally, the surgical instrument includes an
elongated device forming a helical needle and an electrode
associated with the helical needle. The helical needle is
configured to engage bodily tissue. Further, the helical needle is
hollow and is fluidly connected to the fluid source for delivering
the conductive fluid. Finally, the helical needle terminates in a
needle tip. The electrode is associated with the helical needle and
is connected to the current source. With this configuration, during
use, the helical needle is maneuvered into engagement with a
desired location of bodily tissue. Conductive fluid is delivered to
the bodily tissue via the helical needle. The current source is
then activated to supply a current to the electrode, in turn
applying a current to the conductive fluid delivered from the
helical needle. Application of the current to the delivered
conductive fluid creates a virtual electrode, thereby ablating
bodily tissue in contact therewith.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] FIG. 1 is a block diagram of a surgical system for creating
a virtual electrode to ablate bodily tissue in accordance with the
present invention;
[0025] FIG. 2 is an enlarged, side view of a helical needle portion
of a surgical instrument used with the system of FIG. 1;
[0026] FIG. 3 is a side view of an alternative helical needle in
accordance with the present invention;
[0027] FIG. 4 is an enlarged, side view of an alternative helical
needle in accordance with the present invention;
[0028] FIG. 5 is an enlarged, side view of an alternative helical
needle in accordance with the present invention;
[0029] FIG. 6 is an enlarged, side view of an alternative helical
needle in accordance with the present invention;
[0030] FIG. 7 is an enlarged, exploded view of an alternative
helical needle assembly in accordance with the present
invention;
[0031] FIG. 8 is an enlarged, side view of an alternative helical
needle assembly in accordance with the present invention;
[0032] FIG. 9 is an enlarged, side view of an alternative helical
needle assembly in accordance with the present invention;
[0033] FIG. 10 is an enlarged, perspective view of an alternative
helical needle in accordance with the present invention;
[0034] FIG. 11 is an enlarged, perspective view of an alternative
helical needle assembly in accordance with the present
invention;
[0035] FIG. 12 is an enlarged, cross-sectional view of an
alternative helical needle in accordance with the present
invention;
[0036] FIG. 13 is an enlarged, side view of an alternative helical
needle in accordance with the present invention;
[0037] FIG. 14 is an enlarged, cross-sectional view of an
alternative helical needle in accordance with the present
invention; and
[0038] FIG. 15 is an enlarged, perspective view of an alternative
helical needle assembly in accordance with the present
invention.
DETAILED DESCRIPTION OF THE PRESENT INVENTION
[0039] FIG. 1 illustrates in block form a surgical system 20 for RF
ablation useful with the present invention. The surgical system 20
includes a current source of radiofrequency alternating electric
current 22, a fluid source of RF ablating fluid 24, including but
not limited to saline and other conductive solutions, and a
surgical instrument 26 for delivering the RF current and the
ablation fluid to a tissue site (not shown) for ablation purposes.
In one preferred embodiment, the surgical instrument 26 is
connected to the current source 22 and the fluid source 24. It will
be understood that the current source 22 and the fluid source 24
may be combined into a single operational structure controlled by
an appropriate microprocessor for a controlled delivery of ablating
fluid and a controlled application of RF current, both based upon
measured parameters such as but not limited to, flow rate, tissue
temperature at the ablation site and at areas surrounding the
ablation site, impedance, the rate of change of the impedance, the
detection of arcing between the surgical instrument and the tissue,
the time period during which the ablation procedure has been
operating, and additional factors as desired.
[0040] While the surgical instrument 26 is shown as being connected
to both the current source 22 and the fluid source 24, the present
system is not so limited but could include separate instruments for
those purposes. For example, a separate needle or similar apparatus
could be used to deliver the current and a separate needle or
needles could be used to deliver fluid to the target tissue. In
addition, the application of the surgical system 20 illustrated in
FIG. 1 is not limited to the use of straight needles or helical
needles as surgical instruments but could find use with any type of
instrument wherein a conductive solution is delivered to a tissue
and an RF current is applied to the tissue through the conductive
fluid. Such instruments thus would include straight needles,
helical needles, forceps, roller balls, or other instruments for
the treatment of vascular disorders, and any other instrument.
[0041] As described above, the surgical instrument 26 may assume a
wide variety of forms. In accordance with the present invention,
however, the surgical instrument includes an elongated device
terminating in a helical needle assembly configured to deliver the
conductive fluid as well as to apply a current to the so-delivered
fluid. Various embodiments of acceptable helical needle
configurations are shown in FIGS. 2-15. For example, FIG. 2
illustrates one embodiment of a helical needle or helical needle
assembly 30. The helical needle 30 is preferably hollow,
terminating in a needle tip 32 at a distal end 34 thereof. The
needle tip 32 defines an opening (not shown) for delivering
conductive fluid supplied to the helical needle via the fluid
source 24 (FIG. 1). Further, as previously described, the helical
needle 30 is preferably configured to serve as an electrode for
applying a current, via the current source 22 (FIG. 1), to the
delivered conductive fluid. With the above in mind, the helical
needle defines a pitch P between adjacent coils 36 that increases
in the distal direction. This varying pitch facilitates first the
engagement of the needle tip 32 with tissue (not shown) at a target
site and its initial threading therein. As the pitch between
adjacent coils 36 of the helical needle 30 decreases in the
proximal direction, the adjacent coils 36 more tightly engage the
tissue, thereby providing a better seal between the tissue and the
needle coils 36. This greater sealing ability reduces the
likelihood that the conductive fluid, which is heated during the
ablation process to a temperature capable of killing cells, will
not leak back along the track in the tissue made by the helical
needle 30. Thus, the conductive solution will tend to stay closely
adjacent to the needle tip 32 rather than leak backwards along the
needle track and unintentionally and undesirably damage or destroy
other healthy tissue.
[0042] Referring now to FIGS. 3 and 4, alternative embodiments of a
fluid and RF current delivery helical needle 40 and 50 are
illustrated. Both helical needles 40 and 50 are hollow, terminating
in a needle tip 42, 52, respectively, and have a variable diameter
that changes in the proximal to distal direction. In the case of
the helical needle 40, an outer diameter of the helical needle 40
increases in the proximal to distal direction, whereas with the
helical needle 50, the outer diameter decreases in the proximal to
distal direction. Varying the diameter in this manner may allow for
better sealing of the tissue (not shown) in the affected region
against the coils comprising the respective helical needle 40 or
50. That is, alternating the diameter in the manner shown increases
the loading of the tissue across the various coils unlike a
uniformly coiled needle, wherein the tissue loading is uniform
across the coils. Varying the diameter will also affect the amount
of torque that must be applied by a surgeon to screw the needle tip
42, 52 into the tissue to be ablated. Thus, with respect to the
helical needle 40, as the helical needle 40 is turned into the
tissue, the torque necessary to rotate the needle tip 42 increases
because the coils force the engaged tissue into a smaller diameter,
thus substantially sealing a resulting needle track against leakage
of heated conductive fluid there along. Similarly, with respect to
the helical needle 50 as shown in FIG. 4, the helical needle 50
first engages a relatively small portion of tissue and subsequently
forces the larger diameter coils into the same needle track as
followed by the initially small diameter needle tip 52.
[0043] Referring now to FIG. 5, an alternate embodiment of helical
needle 60 useful in an RF ablation procedure is shown. As with
previous embodiments, the helical needle 60 is hollow to provide a
flow path for conductive fluid, and defines a needle tip 62 through
which the conductive fluid exits the helical needle 60.
Additionally, the helical needle 60 has a diameter that first
increases in the proximal to distal direction and then decreases to
a diameter somewhat similar to the initial coil diameter at the
needle tip 62.
[0044] Yet another alternative embodiment of a helical needle 70 is
shown in FIG. 6. The helical needle 70 has a coil diameter that
decreases in the proximal to distal direction for a predefined
predetermined distance and then increases to a diameter
substantially equal to the original diameter. Once again, the
helical needle 70 is hollow and has a needle tip 72 defining an
opening for the outflow of conductive fluid. Both of the
embodiments 60 and 70 shown in FIGS. 5 and 6 provide for a varying
torque and increased sealing ability due to the action of the
helical needle 60 and 70 forcing the tissue (not shown) to follow
the coils through the tissue as the diameter thereof varies.
[0045] Yet another alternate embodiment of a helical needle
assembly 80 is shown in exploded view in FIG. 7. The helical needle
assembly 80 comprises a plurality of concentric helical needles 82,
84 and 86. Alternatively, only two such helical needles could be
provided or additional helical needles may be used as desired. The
use of a plurality of concentrically disposed helical needles 82,
84 and 86 allows the physician to engage thinner tissues (not
shown), such as the atrial wall. The concentric helical needles 82,
84 and 86 are preferably wound in the same direction to facilitate
insertion and capture of the tissue. Each helical needle 82, 84 and
86 includes a needle tip 83, 85 and 87, respectively. As desired,
the helical needles 82, 84 and 86 are hollow to provide a fluid
path for conductive fluid from the fluid source 24 (FIG. 1) with
the fluid exiting through needle tips 83, 85 and 87 respectively.
That is, one or more of the helical needles 82, 84 or 86 could be
used to provide fluid to the tissue to be ablated. Additionally,
one or more of the helical needles 82, 84 or 86 may be used as a
suction path for removal of conductive fluid.
[0046] Yet another alternative embodiment of a helical needle
assembly 90 is depicted in FIG. 8. In general terms, the helical
needle assembly 90 comprises a plurality of helical needles, here
92 and 94, wound parallel to one another. As with previous
embodiments, each of the helical needles 92 and 94 are preferably
hollow, terminating in an open, needle tip 96 and 98, respectively.
The use of a parallel assembly would enable the physician
performing an ablation procedure to use one of the helical needles
92 or 94 as a fluid path for providing conductive fluid from the
fluid source 24 (FIG. 1) to the tissue (not shown) to be ablated
and the second helical needle 92 or 94 as a vacuum source for
removal of the conductive fluid. The use of suction to remove the
ablation fluid either during or at the end of the procedure will
reduce the likelihood of leakage of the hot conductive fluid
backwards along the needle track.
[0047] Yet another alternative embodiment of a helical needle
assembly 100 is shown in FIG. 9. The helical needle assembly 100 is
similar to the helical needle assembly 80 (FIG. 7) previously
described. The helical needle assembly 100 includes outer and inner
helical needles 102 and 104 concentrically arranged. As with the
embodiment shown in FIG. 7, the concentric helical needles 102, 104
may be used to deliver fluid at different depths in a tissue (not
shown) or one or more flow paths could be used to provide suction
and removal of the ablating solution from the tissue during or
subsequent to the termination of the application of RF power to the
tissue, via the current source 22 (FIG. 1). As shown in FIG. 9,
only two such concentric helical needles 102, 104 are shown, though
multiple coils in excess of two could be used.
[0048] It will be understood that the various configurations could
be combined in several of the embodiments shown. For example, the
variable pitch shown in FIG. 2 could be combined with the variable
diameters shown in FIGS. 3-5 and 8. In addition, the variable
diameter structure shown in FIGS. 3-6 could be combined with the
parallel assembly construction shown in FIG. 8.
[0049] Referring now to FIGS. 10 and 11, alternate embodiments of
helical needle assemblies 110 and 120, including alternate means of
anchoring a needle to a tissue (not shown), are shown. With
reference to FIG. 10, the helical needle assembly 110 is an
archimedes type screw comprising a central shaft 112 about which a
helical flight 114 is wound. The central shaft 112 is preferably
hollow for delivering conductive fluid from the fluid source 24
(FIG. 1). The helical needle assembly 120 has a substantially
straight fluid and current delivery portion 122 mounted
substantially centrally of a disc 124 having a plurality of
starting threads 126. The starting threads 126 will engage the
tissue (not shown), such as a cardiac wall, and will anchor the
helical needle assembly 120 thereto. Though it be understood that
the straight needle portion 122 would penetrate the tissue wall to
deliver fluid and electric current from the fluid source 24 (FIG.
1) and the current source 22 (FIG. 1), respectively.
[0050] In the discussion of FIGS. 2-11, it has been understood that
each embodiment described would deliver conductive fluid through a
single aperture at the needle tip. The present invention is not so
limited however. Thus, the fluid could be delivered to the tissue
(not shown) by laser drilling a plurality of holes along the length
of the various coiled needle configurations. These laser drilled
fluid delivery apertures could be configured as desired in terms of
size and well as number and distance from each other along the
longitudinal extent of the helical needle. FIGS. 12-14 illustrate
yet additional fluid delivery methods. Thus, as shown at FIG. 12, a
helical needle 130 could include openings 132 extending along part
of an outer diameter of the helical needle 130. Alternatively, a
helical needle 140 is shown in FIG. 13 as including an open slit
142 extending along an outer diameter thereof. Conversely, a
helical needle 150 is depicted in FIG. 14 as having a coil
structure wherein a fluid delivery aperture or slit 152 extends
along the inner diameter of the needle coils.
[0051] FIG. 15 illustrates yet another alternative embodiment of a
helical needle assembly 160 in accordance with the present
invention including a pair of concentric helical needles 162 and
164. The first helical needle 162 is a large diameter needle whose
end 166 (shown partially) is used to anchor the instrument in
tissue 168. The second helical needle 164 has a smaller diameter
than the first helical needle 162 and is disposed substantially
coaxially therewith. Each of the helical needles 162 and 164 may
include a hollow interior to provide a flow path for conductive
fluid from the fluid source 24 (FIG. 1) and each could be
electrically active, via the current source 22 (FIG. 1), through
known appropriate connections. Either or both of the helical
needles 162, 164 may be used to deliver conductive fluid and either
of the helical needles 162, 164 could be electrically active.
Alternatively, the helical needles 162 and 164 could form a bipolar
needle wherein the helical needles 162, 164 have opposing
polarities and the current provided by one travels to the
other.
[0052] Although the present invention has been described with
reference to preferred embodiments, workers skilled in the art will
recognize that changes may be made in form and detail without
departing from the spirit and scope of the invention.
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